Refrigeration apparatus



July 8, 1941. L. F. WHITNEY REFRIGERATION APPARATUS 2 SheetsSheet 1 Filed Dec. 2, 1937 July 8, 1941. F. WHITNEY REFRIGERATION APPARATUS Fileql Dec. 2, 1957 Sheets-Sheet 2 I fizbfewr lymz o Wjy w .s.

fwd! M Patented July 8, 1941 REFRIGERATION APPARATUS Lyman F. Whitney, Cambridge, Mass asslgnor, by mesne assignments, to Stator Corporation. a corporation of Rhode Island Application December 2, 1937, Serial No. 177,749

6 Claims.

This invention relates to improved pumping assemblies of the aspirator type, particularly the two-stage type. Such pumping assemblies are provided with means to supply propellant vapor to an aspirator nozzle from which the vapor issues at high speed to entrain molecules of a gas or vapor received from a vessel which normally is maintained at a relatively low pressure by the pumping means and to pump the vapor thus received to a pressure substantially greater than its initial pressure but to a pressure which is substantially lower than that of the propellant vapor received by the nozzle. More particularly pumping assemblies of this type may be employed in refrigerating apparatus of the general type disclosed in United States Patent No. 1,761,551 of Eastman A. Weaver.

Such an apparatus may comprise a boiler arranged to supply a stream of propellant vapor, e. g., mercury vapor to an aspirator nozzle or nozzles. Each aspirator nozzle is arranged to emit the vapor at high speed into a mixing chamber which may be connected by a vapor duct to the cooler of the refrigerating system or to the outlet of a first stage aspirator. The mercury vapor thus received by the mixing chamber is effective in entraining the refrigerant vapor which may be water vapor or a mixture of the vapor of water and a suitable anti-freeze agent. The mixed vapors then flow into an elongate funnel which is provided with a bore aligned with the nozzle. In the funnel the refrigerant vapor is compressed and condensation of propellant vapor takes place. The pumped vapor leaving the funnel normally has a pressure substantially greater, 1. e., at least several times as great as its pressure when it was received by the mixing chamber, although this pressure of the pumped vapor at the outlet of the funnel may be but a minor fraction of the pressure of the mercury vapor received by the nozzle. In the case of twostage pumping the first funnel delivers into a second mixing chamber which has associated therewith a second nozzle and a second funnel. The pressures, in terms of millimeters or mercury absolute, may be as follows:

Full

Average load load I have found that by suitable arrangements of the bore of the funnel must be suitably proportioned and arranged relative to the nozzle. It is particularly advantageous to provide the bore of the funnel with a relatively long, gradually tapered portion extending from its inlet end to a throat where the bore has a minimum diameter, and to arrange this tapered portion of the bore so that the angle of its taper is substantially less adjoining the throat than adjoining the funnel inlet. It will be evident that by the term gradually tapered, I mean to indicate that the diameters of adjoining portions of the bore may only differ slightly from each other while the angle of the taper may be uniform or may differ slightly at difierent parts of the bore. For example, the tapered portion of the funnel is pref erably provided in two tapered sections, a first section extending from the inlet end of the funnel and a section between the first section and the throat of the funnel. Each section preferably has a substantially uniform taper, although the two sections may be joined together by a sectibti of gradually changing taper and the taper or each section may gradually decrease. Referring to the percentage of taper (or flare) as the tangent of the acute angle defined by a longitudinal line in the wall of the section and an intersect ing line parallel to the axis of the section. the first section has a greater percentage of taper than the second section; preferably the taper oi! the second section is only a few per cent and the taper of the first section is at least approximately five times as much. Also the first section is preferably only approximately half as long as the second section,

The funnel should also have a gradually flared section extending from-its throat to the outlet of the funnel, i. e., to the duct section of uniform diameter which receives the pumped fluid from the funnel. The preferred shape of the flaring section is as follows: Percentage of flare approximately five in each stage; ratio of length of the section to the diameter of the throat of the funnel, approximately ,ten in the first stage and twenty in the second stage; and ratio of said length to the diameter of the throat being approximately twice the percentage of flare in the first stage and approximately four times the percentage of flare in the second stage.

I have also found it advantageous in apparatus of this character to provide a mixing chamber of substantial diameter and also of substantial extent longitudinally of the funnel with the inlet end of the funnel projecting into this chamber for the major portion of the longitudinal extent of the chamber. It is also preferable to have the nozzle project into the mixing chamber but to have the ends of the nozzle and funnel spaced from each other at a distance at least of the order of the diameter of the throat of the funnel bore.

For satisfactory emciency it is necessary to cool the more gradually tapered portion of the funnel and when this portion begins near the entrant end of the funnel, as in the second stage of the illustrative embodiment hereinafter discosed, this invention involves sloping that wall of the mixing chamber which surrounds the funnel inwardly toward the nozzle, as by making it in the form of a. reentrant cone, thereby producing an effect equivalent to having the funnel project into the mixing chamber and at the same time permitting the funnel to be cooled substantially to its inlet end.

Another salient feature of the invention consists in making the outlet end of the nozzle many times larger than the throat of the nozzle. For example, the ratio of the two areas may be of the order of between thirty and fifty to one in the first stage and between five and ten to one in the second stage; in the illustrated embodiment hereinafter disclosed they are approximately thirtyelght and six.

For maximum efficiency the pressure of the mercury vapor at the outlet end of each nozzle should be equal to the pressure in the corresponding mixing chamber, thereby producing a state of pressure equilibrium in the region where mixture takes place. However, the pressures in the mixing chambers vary throughout ranges depending upon changes in operating conditions, such as might be caused by changes in room temperature or changes in the setting of the control dial, the range in the first-stage mixing chamber corresponding to the range of pressures in the cooler or evaporator and the range in the second-stage mixing chamber being higher. Consequently, to

' attain maximum efficiency when most needed, the

first-stage nozzle is preferably shaped and proportioned to effect the aforesaid state of equilibrium in its mixing chamber when the pressure in the evaporator is at the lower end of its range, and the second-stage nomle is shaped to have an outlet pressure in equilibrium with the pressure to which the first-stage aspirator will pump vapor eiliciently when the pressure in the evaporator is at the lower end of its range.

A further feature involves novel means for keeping the nozzle in alignment with the funnel while permitting longitudinal expansion and contraction of the nozzle throughout changes in temperature during successive stages of operation.

A further feature of the invention relates to the provision of novel, compact and efficiently cooling means for the funnel, thus permitting the effective condensation of spent mercury particles in the funnel and particularly adjoining the wall thereof. The present invention afiords a cooling means of this character which is effective over a wide pumping range. For this purpose the funnel may be provided with a Jacket containing a suitable coolant, the jacket forming part of a hermetically sealed cooling system. This cooling system may conveniently comprise a condenser section which receives coolant vapor from the jacket. To permit this desirable result, the cooling system may conveniently be evacuated so that the pressure to which the coolant is normally subjected is substantially below atmospheric pressure. The condenser section of the cooling system may conveniently be provided with a tube having cooling iins thereon and with a closed chamber of substantial volumetric capacity connected to the tube. Accordingly, economy in cost of manufacture is permitted and the space required for installation of this system may be smaller than would otherwise be necessary.

In the accompanying drawings:

Fig. 1 is an elevational view somewhat diagrammatic in character and with parts broken away, showing a refrigerating system in which my improved pumping means is employed;

Fig. 2 is an end view of the first-stage aspirator;

Fig. 3 is a sectional view with parts shown in elevation illustrating the first-stage pumping unit; and

Fig. 4 is a similar view illustrating the secondstage pumping unit.

While pumping units of the character disclosed herein may be employed in a variety of environments where it is desired to produce a relatively low pressure by drawing vapor or other gas of low molecular weight from a suitable chamber as from the evaporator of a refrigerating system, the arrangement disclosed herein is of particular advantage when employed in a low pressure refrigerating system of the type disclosed in the above-identified patent. Accordingly, for purposes of illustration, my improved pumping assembly is shown in association with such a system in the accompanying drawings.

A refrigerating system of this character may comprise a boiler i containing a body of propellant liquid, preferably mercury, and having a suitable heating unit, such as a burner 2, provided with a stack I for exhaust gases. A riser duct 4 extends upwardly from the boiler i and is provided with branches 4* and 4 respectively, for supplying mercury vapor to the first-stage and second-stage pumping assemblies 8 and B, respectively, The mercury vapor from the duct 4" is received by the nozzle ll of the first-stage assembly S and is emitted at high speed into the substantially cylindrical mixing chamber II. The latter is connected by a suction or vapor duct I2 to a cooler I3 containing a body of liquid refrigerant. This refrigerant may conveniently be water or a mixture of water and a suitable volatile anti-freeze agent. In any case it is desirable to provide refrigerant in the cooler I3 which may supply vapor to the duct i2 which has a molecular weight that is much less than the molecular weight of the propellant vapor. The mixed vapors iiow from the mixing chamber Ii into the funnel I! where a portion of the propellant is condensed and where the pressure of the pumped refrigerant is increased.

From the funnel l5 the pumped vapor may pass into an inter-stage cooler l8 which is connected by a duct ll to the inlet it of the secondstage pumping assembly 8 The latter is provided. with a nozzle III which receives mercury vapor from the duct 4'' and supplies the same to the mixing chamber II. The mixed vapors flow into a funnel I! (Fig. 4) from which the compressed refrigerant vapor may pass into a duct 20 and thence to the condenser 2| which is provided with any suitable cooling means. The refrigerant vapor is liquefied in condenser 2| and the resulting condensate may drain through a return duct 22 and bubble through a mercury containing trap 22 at the lower end of this duct which is connected to the cooler. Thus, the refrigerant completes its circuit.

A propellant drain 2'! is arranged to receive condensed propellant which flows downwardly from the lower end of the inclined funnel ll of the first-stage pumping assembly 8. The lower end of this drain 2'! which provides a pressurebalancing trap is connected to a drain 28 which receives condensed propellant from the secondstage assembly -S Drains 29 and 30 are connected to the mixing chambers II and Il' providing a pressure-balancing trap therebetween and supplying condensed propellant from these chambers to one leg of a trap 3|, the opposite leg of which is connected to the lower part of the drain 28. A continuation of the drain 28 provides a return duct 33 containing a column of condensed mercury to balance the boiler pressure and being arranged to supply mercury to the lower part of the boiler I.

In practice I prefer to operate a system of this character at a low pressure. For this purpose the system may be initially evacuated through a sealing device 35 of the type fully disclosed and claimed in my copending application Serial No. 136,612, filed April 13, 1937. During normal operation of the apparatus, the boiler pressure may be of the order of atmospheric pressure or less, while the pressure in the cooler l3 may be of the order of less than 10 millimeters of mercury absolute and the pressure in the condenser 2|, varying in accordance with the temperature of the' surrounding air or other cooling medium, may be of the order of from 15 to 120 millimeters absolute.

As shown in Figs. 2 and 3 each nozzle is held in accurate alignment with its funnel by means of a rod comprising two parts H and I2 and a ball 13. The part II threads into the rear end of the nozzle and is threaded over the forward end of the part 12. The ball 13 is rigidly attached to a ring 14 which in turn is rigidly mounted on the mixing chamber. The central portion of the ball is provided with a bearing plug 15 in which the part 12 snugly slides, thereby to permit axial movement of the rod and nozzle in response to expansion and contraction as the parts are heated and cooled throughout successive stages of operation. The rod or bail or both are preferably formed of nichrome, stainless steel or other material of low conductivity, thereby to reduce the heat loss.

Owing to the high velocity of the mercury vapor flowing from the outlet end of each funnel the globules of mercury tend to cut through the opposing wall and to counteract this tendency I propose to provide an insert of hard material such as Stellite No. 1. As shown in Fig. 4, this insert may comprise a disk 16 welded to the bottom .of a cup-shaped plug 11 which is fitted into the end of the funnel l and welded at 18.

My improved pumping means is especially advantageous in providing a relatively eflicient aspirator assembly for use with a low inlet pressure in the mixing chamber and consequently a low pressure in the cooler or the like, and to compress the pumped fluid, e. g., the refrigerant vapor, to a pressure substantially higher than the nozzle outlet may be of the order of five to six times the diameter of its throat, the throat of the nozzle having a diameter which is a minor fraction of the diameter of the throat T of the funnel, and the outlet of the nozzle preferably having a diameter which is somewhat greater, e. g., approximately 1.2 times that of the throat of the funnel. As shown, the nozzle preferably projects slightly into the mixing chamber II. This chamber I l preferably has a relatively large diameter; for example this dimension may conveniently be of the order of seven to ten times the diameter of the funnel throat. The inlet portion of the funnel also projects for a substantial distance into the mixing chamber. Thus, as shown in Fig. 3, the extent of this projection may be greater than one-half the maximum dimension of the mixing chamber which extends longitudinally of the funnel. On the other hand, it is desirable to space the end of the funnel from the end of the nozzle, this spacing being at least of the order of the diameter of the throat of the funnel.

An important feature of the invention pertains to the arrangement of the tapered sections of the hereof the funnel. In accordance with this invention, the portion of the funnel extending from its inlet to its throat T, i. e., its portion of minimum internal diameter, is gradually tapered with the taper being less adjoining the throat than adjoining the inlet. Preferably, as shown, this tapered portion of the funnel may be provided in two sections, each of which has its own uniform taper. The first section of the funnel may have an inlet diameter nearly four times as great as the diameter of the funnel throat, while the diameter of the funnel at the junction J of the first and second tapered sections may be of the order of twice the diameter of the throat, which have a junction at J (Fig. 4). The length of the first section may be of the order of eight to twelve times the diameter of the funnel throat, while the length of the second section may be of the order of fifteen to twenty times this dimension. The bore of the funnel is also provided with a third flaring section or portion which increases in diameter as it extends away from the throat to its outlet portion which is connected to the inter-stage cooler. The outlet end of this third tapered section of the funnel may have an internal diameter at least of the order of twice the diameter of the throat, and this section may have a length of the order of five to ten times the diameter of the throat.

The arrangement of the second-stage assembly and the approximate proportions of the component parts thereof are shown more particularly in Fig. 4 from which it is evident that the funnel I 5 may project into the mixing chamber II' to the same general extent as the tunnel l5 projects into the mixing chamber I i. The nozzle l0, while smaller than the nozzle I0, is similarly tapered and has an outlet diameter at least twice as great as the diameter of its throat. The ends of the fimnel and the nozzle are also spaced from each other at a distance which is greater than the minimum diameter of the bore of the funnel, i. e., the diameter of the throat T of the funnel. This funnel also preferably is provided with two gradually tapered sections between its inlet end and its throat. tion may have a diameter approximately twice as great as the diameter of the funnel throat, while the diameter of the smaller end of this section of the funnel and of the larger end of the adjoining more gradually tapered section may be greater than that of the throat of the funnel but less than 2.5 times this dimension.

The flaring section of the funnel which extends from its throat to its outlet may have a length between ten and twenty times the diameter of the throat and the diameter of the larger end of this section of the funnel bore preferably is at least twice as great as the diameter of the funnel throat.

In the preferred embodiment of the invention shown in the drawings the dimensions and shapes are substantially as follows:

1st stage 2nd stage Diameter of nozzle throat inches.. 0705 0635 Area of nozzle throat .square inches.. 0038 0032 Length of nozzle from throat to outlet end inches. l. 297 382 Diameter of outlet end of nozzle ..do. 435 161 Area of outlet end of nozzle ..square inches i485 02 Flare nozzle ..peroent. 14. 3 14.1 Distance from outlet end of n zle t inlet en funnel inclies 471 329 Diameter of inlet end of iunneL do 1% 377 Length of first tapered section do 3. 710 507 'laper of first section ..percent.. 10. 5 14.4 Diameter at junction between the two tapered sections .inches. 623 284 Length of second tapered section ..do.. 6. 2 1.08 'laper of second to red section percent 2 2 Diameter of [dune throat "inches" .357 .180 Length of flaring section of funnel do 3. 25 3. 60 Flare of flaring section of funnel percent. 5 5

While for purposes of particularity of disclosure I have referred in some detail to the relationship between certain dimensions of the first and second-stage pumping assemblies which I have found to have an important eflect on the pumping eificiency of the apparatus, it is to be understood that other dimensional relationships and the general proportioning of parts, illustrated but not specifically referred to, also have been found advantageous. I have described in some detail important inter-dimensional relationships of the component pants of two pumping assemblies, and the general factors determining these relationships in the two assemblies may be regarded as determining especially significant attributes which have a material effect upon the efllciency of the pumping apparatus.

The pumping amembly S is provided with a cooling system which may be conveniently hermetically sealed by a device 35' similar to the device 35 upon the condenser of the refrigerating system. This cooling system includes a jacket 60 surrounding the funnel l5 which latter may be provided with a plurality of cooling fins 6| to aid the transfer of heat from the funnel to a body of volatile liquid contained within the jacket. As a practical matter, I prefer to evacuate the cooling system and to dispose a body of liquid such as alcohol in the system which will be readily volatile under the pressure The larger end of the first secaesaeeo and temperature conditions which prevail when the system is in operation. The jacket II is connected to an upwardly extending duct 02, a portion of which is provided with cooling fins 03 and the end of which communicates with a chamber 04 of substantial volumetric capacity, this chamber 04 supporting the sealing device and evacuating connection 35'. The cooling system for the second stage pumping unit 8 may be generally similar to the system for the first stage unit, and has similarly designated parts with the reference characters primed. However, the finned section of the pipe 62' of the second-stage system may be smaller than that for the first-stage system since the amount of heat which is required to be dumped by this portion is less than in the case of the first-stage cooling system.

It is evident that the present invention affords simple and compact aspirator assemblies for pumping fluid such as refrigerant vapor from a region of low relative or absolute pressure to a region of substantially higher pressure, and that such pumping means is provided with emcient, compact and inexpensive cooling means. I have found that pumping units having component parts with general proportions of the type disclosed herein are especially advantageous in permitting a very substantial increase in pumping efllciency and thus allowing the operation of a system of this character with greater fuel economy for the same refrigerating capacity.

It should be understood that the present disclosure ls for the purpose of illustration only and that this invention includes all modifications and equivalents which fall within the scope of the appended claims.

I claim:

1. An aspirator employing mercury vapor as a propellant for pumping refrigerant vapor from an evaporator to a condenser, comprising a mixing chamber having a connection to receive vapor from the evaporator, a funnel having an inlet end communicating with the mixing chamber and having an outlet end from which vapor may pass, and a mercury-vapor nozzle communieating with the mixing chamber in axial alignment with the inlet end of the funnel, a jacket surrounding the funnel, the funnel being joined to the surrounding wall of the mixing chamber which wall slopes inwardly toward the nozzle to provide a re-entrant end of the jacket surrounded by the mixing chamber, so that the entrant end of the funnel may be cooled with a circulating cooling medium.

2. An aspirator employing mercury vapor as a propellant for pumping refrigerant vapor from an evaporator to a condenser, comprising a mixing chamber having a connection to receive vapor from the evaporator, a funnel having an inlet end communicating with the mixing chamber and having an outlet end from which vapor may pass to the condenser, and a mercury-vapor nozzle communicating with the mixing cham ber in axial alignment with the inlet end of the funnel, the funnel and nozzle having throats spaced from the ends of the funnel and nozzle which adjoin each other, the cross-sectional area of the outlet end of the nozzle approximating that of the funnel throat and being many times that of the nozzle throat, :the funnel having a portion in advance of its throat which tapers only a few per cent and a portion in advance of said portion which is approximately half as long and which tapers more, the last-named portion or the tunnel extending substantially to the inlet end of the funnel and having a length greater than the length of the nozzle between its throat and outlet end.

3. An aspirator for pumping refrigerant vapor from an evaporator to a condenser, comprising a mixing chamber to receive vapor from the evaporator, a funnel having an inlet end communicating with the mixing chamber and having an outlet end from which vapor may pass to the condenser, and a propellant noule communicating with the mixing chamber in axial alignment with the inlet end or the funnel, the tunnel and nozzle having throats spaced from the ends of the funnel and nozzle which adjoin each other, the cross-sectional area of the outlet end of the nozzle approximating that of the funnel throat and being many tima that of the nozzle throat, the funnel having a portion in advance of its throat which tapers only a Iew per cent and a portion in advance or said portion which is approximately half as long and which tapers at least approximately five times as much, the last-named portion of the funnel extending substantially to the inlet end of the funnel and having a length greater than the length of the nozzle between its throat and outlet end.

4. An aspirator for pumping refrigerant vapor from an evaporator to a condenser, comprising a mixing chamber to receive vapor from the evaporator, a funnel having an inlet end communicating with the mixing chamber and having an outlet end from which vapor may pass to the condenser, and a propellant nozzle communicating with the mixing chamber in axial alignment with the inlet end of the funnel, the funnel and nozzle having throats spaced from the ends of the funnel and nozzle which adjoin each other,

the cross-sectional area of the outlet end of the nozzle approximating that oi the funnel throat and being at least approximately six times that of the nozzle throat, the tunnel having a portion in advance of its throat which tapers only a few per cent and a portion in advance of said portion which is approximately half as long and which tapers at least approximately flve times as much, the last-namedportion of the tunnel extending substantially to, the inlet end of the funnel and having a length greater than the length of the nozzle between its throat and outlet end,

5. An aspirator employing mercury vapor as a propellant for pumping refrigerant vapor from an evaporator to a condenser, comprising a mixing chamber having a connection to receive vapor from the evaporator, a funnel having an inlet and communicating with the mixing chamber and having an outlet end from which vapor may pass to the condenser, and a mercury-vapor nozzle communicating with the mixing chamber in axial alignment with the inlet end of the funnel, the tunnel and nozzle having throats spaced from the mixing chamber, the cross-sectional area of the outlet end of the nozzle approximating forty times that of the nozzle throat,

the tunnel having a portion in advance of its throat which tapers only a few per cent and a portion in advance of said portion which is approximately hali! as long and which tapers more, the last-named portion of the funnel extending substantially to' the inlet end of the tunnel and having a length greater than the length of the nozzle between its throat and outlet end.

6. A two-stage aspirator assembly receiving mercury vapor as a propellant from a common source and for pumping refrigerant vapor from an evaporator to a condenser, the first stage 01 the assembly comprising a mixing chamber, a tunnel communicating with the mixing chamber, a propellant nozzle communicating with the mixing chamber in axial alignment with the inlet end of the funnel, the funnel and nozzle having throats spaced from each other, the cross-sectional area of the outlet end of the nozzle approximating that of the funnel throat and being approximately forty times that of the nozzle throat, the second stage aspirator comprising a Y mixing chamber, a funnel and a nozzle, the crosssectional area of the outlet end of the second stage nozzle approximating that of the second stage tunnel throat and being at least approximately six times that of the throat of the second stage nozzle, each of. the tunnels having a portion in advance of its throat which tapers only -a few per cent and having a portion in advance of said portion which is of less length and which tapers more than said first portion.

- LYMAN F. WHITNEY. 

